Pitchograph



Oct. 26, 193

7. w. R. KEAR PITCHOGRAPH Filed Oct. 2'7. 1936 INVENTOR W R. KEAR ATTORNEY Patented Oct. 26, 1937 UNITED STATES PATENT 7 Claims.

(Granted under the act of amended April 30, 1928;

This invention relates to means for developing thedesign pitch of a propeller pattern, and has among its numerous objects;

To provide a simple apparatus for quickly and accurately developing the design pitch of a propeller pattern;

To provide mechanism that will eliminate the necessity of constructing a pitch template and pitch rail, using the pitch rail to locate'points on the curve that will define a portion of the face of 'the pattern and then defining the curve through the several points by a flexible straight edge;

To expedite and facilitate the layout and construction of propeller. patterns.

In the drawing:

Fig. 1 is an elevational view of one structural embodiment of my present invention;

Fig. 2 is a top plan view disclosing diagrammatically the positions of the gears in the gear train hereinafter to be described.

The use andsignificance of my invention may best be made clear by setting forth the method of constructing propeller; patterns as heretofore practiced. The pattern maker constructs a template of Wood about thick according to dimensions given on the drawing, the template being in the form of a right triangle with its hypotenuse at the desired pitch angle. A circle of convenient diameter is then scribed on the layout table and a number of perpendicular stanchions set to the circle and properly braced,

after which the template is clamped to the' stanchions. The pitch rail, a strip of hard wood about 2" wide and thick',1is placed on the hypotenuse of the template and screwed to the stanchions, after which the template is removed and the tops of the supports are cut off flush with the upper edge of the pitch rail.

The pattern for the hub is then built up concentrically with the circle above mentioned and a cant or lag is fastened in approximate position on the hub pattern. The cant is a piece of wood plank of suitable thickness and is disposed with its wide face substantially perpendicular to a radius of the circle and is so positioned that a curve defining a portion of the face of the pattern will lie wholly in the wide face. The pattern maker then lowers a so-called pitchometer arm until a roller thereon rests upon the pitch rail and a pointer carried by the arm is slid into contact with thelag to make an indentation at the position of the first point in the curve. This arm is a heavy structure that requires a counterbalance of about 700 pounds and is mounted for March 3, 1883, as 370 o. G. 757) pivotal motion concentric with the above mentioned circle. After the point is established the arm is swung in a horizontal plane sov that the pointer moves through a circular arc 2",or 3" long, the arm is lowered until the roller again *5 contacts the pitch rail and a second point is established. These steps are repeated until 15 points have been determined and then small brads are driven into the holes made by the pointer, a thin straight edge is secured in contact 10 with all the brads,'and a line is scribed along the straight edge. The lag'is then worked down to the line, a second lag secured in place and the above steps repeated to determine the curve on the second lag. This is continued until the pattern for the blade has reached the required length 'for'the propeller blade. Extreme care must be exercised not to apply unnecessary pressure to the arm, since that would result in the inaccurate placing of the point determined bythat setting.

My invention eliminates the necessity for constructing the template, setting up the stanchions, fixing the pitch rail thereto, locating the points individually and. defining the curve through those points by means of the flexible straight edge.

As shown in Fig. 1, my apparatus comprises a suitable base 3 having on it a ball bearing'race 4 cooperating with a race 5 secured to the flange 6 at the base ofthe member I, the said member being retained in position on the base by theangle member 8 secured to base 3 and extending over flange 6. The upper end of member '5 is rotatable in a plate 9 that is held against rotation by a member ID extending fromplate 9 to base 3,

which also serves as a brace to steady the apparatus. The wall of member 1 is provided with longitudinally extending slots H in diametrically opposite portions thereon, the lugs 52 and I3 fixed to traveling nut M being disposed in the slots H. The nut It is in threaded engagement with a screw l5 mounted in plate 9 for rotation independently of the member 7, which rotation of member I is effected by a worm gear it fixed to member I and a worm ll rotatably mounted in ears I8 on plate 9 to mesh with the worm gear I6. The supporting arm, designated in its entirety by 20, has the separable bearings 2i and 22 disposed around the member 1 to be slidable thereon and has the portion 23 fixed to lug l3 of travel- 00 ling nut l4 whereby the arm 28 is caused to move along the member I by rotation of screw I5 and is-likewise caused to rotate with the member 7 by engagement of the lugs 52, and l 3 with the walls of the slots H. The arm 20 has a horizontal the pinions and yet permit free longitudinal 'worm gear fixed to the said a last mentioned two gears.

member 24 upon which is slidably mounted a scriber carriage 25 carrying, scribers 26 and a bracing portion 21 to prevent sagging or flexure of the portion 24.

A shaft 28 is mounted at its upper end in a bracket 29 supported on plate 9 and extends 7 through the plate 9, the hand wheel 30 beingfixed The shaft 28 has keyway 3| torcooperto the lower end thereof. formed in it a longitudinal ate with keys in the pinions 32 and 33 to drive movement of the pinions by means of the lever 34 to which are fixed the yokes 35 having arms lying between the pinions 32 and 33 and the collars 36 fixed to the hubs of the pinions, is slidably mounted in plate 9 and'is provided with a plurality of notches3'l, 38 by a pivoted latch 40 to mesh with bevelled gear ions 32 and 33 out of engagement with gear 4| and to hold pinion 33in engagement with gear 4|, respectively. It is apparent that the direction of rotation imparted to worm gear I6 by worm IT to which the gear 4| is connected when the pinion 33is in mesh with gear 4| will be opposite to that when pinion 32 is in mesh with'gear 4| and also that when neither pinion is in'mesh therewith the member I may be rotated freely for positioning the arm 20.

Fixed to the'upper end of shaft 28 is a gear 42 meshed with an idler 43 which is also'meshed with gear 44 secured on the screw I5. .The gears 42 and 44 are readily removable to substitute others having'different numbers of teeth' to vary the gear ratio of the train, the idler 43 being carried on an adjustable bracket 45 to make possible bringing the gear 43 into mesh with the gears 42 and 44' regardless of the relative sizes ofthe It will now be seen that rotation of the shaft 28 by means of hand wheel 33 will, through gear 4|, worm l1 and worm gear i6, cause member I to rotateand swing arm 20 in azimuth and simultaneously, through the train of gears '42, 43 and 44, the screw |5 vwilli be rotated and cause the travelling nut l4 to move 111p or down and thereby impart vertical movement to arm 20, which vertical movement may be given a rate having any desired ratio to the'rate of movement of the arm 2|) in azimuth merelyby providing the proper gear ratio in the gears 42 and 44.

When the propeller blade pattern is to be made,

. gears havingthe proper ratio to cause the arm'zfl to describe therequired helix are used at 42 and 44, the scriber 26 is moved intocontact with the cant at the initial point of the curve and the hand wheel 30' is rotated; thereby causing the arm 20 to swing in azimuth and vertically, the scriber being kept in contact with the face of the lag throughout the movement necessary to describe .7 'the length of curve corresponding to the width of the propeller blade at that particular cross 'section. The lag is then worked down'to the curve, another lag is fastened thereto and the process repeated until the complete pattern has been made. It-is possible to use my apparatus for scribing the curves corresponding to various positions on the blade upon a sheet of paper or other suitable material and then transfer the curve to the lag, it being necessary merely to set the surface upon which the curve is tobe scribed at'the radial distance from the axis of member 1 corresponding to the distance of the particular part of the blade being'laid out from the axis of the propeller.

The lever 34 and 39 engageable. hold the pinion. 32 in. 4|, to hold both pin-'- The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A device of the class described, comprising a rotatably mounted hollow member having longitudinally extending slots in diametrically opposed portions of the wall thereof, a plate fixed against rotation mounted on one end of said member, a end of said member, a worm carried by said plate to cooperate with saidgear, a screw mounted in said plate for rotation independently of said member, a traveling nut on said screw having portions extending through said slots, a supporting arm structure carried by said portions, scribing means adjustablymounted on said arm for movement toward or away from said member, a bevel gear operatively'connected to said worm, a rotatable shaft mounted to lie transversely'of the axis of said worm, bevel pinions slidably mounted on said shaft to be driven thereby and to be selectively engageable with said bevel gear, and a gear train between said shaft and said screw, the gears of saidtrain being readily removable and replacedriving means connecting said screw to, said shaft, other means associated with said shaft selectively to drive said worm in either of two directions, and a scriber slidably mounted on said arm for movement toward and away from said member. 7 i V l 3.' A device of the class described,'comprising a rotatably mounted member, a radially extending arm carried thereby for rotation therewith, a screw carried by said member to be rotatable independently of said member but held against 9 longitudinal movement, a traveling nut on said screw operatively connected to said arm; a drive shaft, means-associated with said shaft to rotate said member, other means associated with said 7 shaft toldrive said screw at a rate having a predetermined ratio to the rate of said member,

and scribing means on said arm movable toward and away from said member. a

4. .A device of the class described, comprising scribing means, a support for said scribing means whereon said scribing means is slidable, means to rotate said support in azimuth, and means interconnected with the last mentioned means simultaneously to move said support vertically at different rates having predetermined ratios to the rate of said movement in azimuth.

5. A device of the class described, comprising scribing means, a support for said scribing means whereon said scribing means is slidable, means including slidably mounted pinions and a gear cooperating therewith to rotate said support in azimuth selectively in either angular sense, and means interconnected with the last mentioned means simultaneously to move said support vertically at difierent rates having predetermined ratios to the rate of said movement in azimuth.

6. A device of the class described, comprising scribing means, a support for said scribing means whereon said scribing means is slidable, means including slidably mounted pinions and a gear cooperating therewith to rotate said support in azimuth selectively in either angular sense, means to hold either of said pinions in mesh with said cooperating gear or hold both of said pinions out of mesh therewith, and means interconnected with said means for rotating said support to move said support vertically at difierent rates having predetermined ratios to the rate of said movement in azimuth.

7. A device of the class described, comprising a support, means to move said support in a helical path, and scribing means carried by said support to scribe a continuous line on a substantially plane surface at right angles to a radius of said helical path, said first mentioned means being selectively changeable to vary the pitch of said helical path. 10

R. KEAR. 

